Blind Snakes of Gorongosa

1 Fevereiro, 2014

Last night’s downpour flushed out a lot of things from under the ground, and one of them was a large blind snake,Megatyphlops schlegelii, which I found as it was swimming in a puddle in front of the Scientific Services’ trailer. Now, large is a relative term – the snake is only a little over a foot long and as thick as a finger, but for blind snakes this is huuuge. Blind snakes, families Typhlopidae and Leptotyphlopidae, comprise some of the smallest reptiles, and definitely the smallest snakes, in the world. In fact, one species, Ramphotyphlops braminus, has spread over the globe with potted plants, mistaken for a small earthworm in the soil.

A comparison of the largest blind snake of Gorongosa, the Giant blind snake (Megatyphlops schlegelii), and the smallest one, the Peter’s thread snake (Leptotyphlops scutifrons)

Both families are considered some of the most basal lineages of snakes, which means that their morphology and behavior gives us some insight into how snakes evolved from their closest relatives, lizards (or, more specifically, clade Toxicofera, which includes monitor lizards, agamas, and a few other groups). They are all subterranean and their morphology reflects this fact in the small but massively calcified skull, hard “beak” made of thick scales that allows them to push through the soil, and incredibly smooth body that minimizes frictions as they tunnel underground. The eyes are vestigial, hidden under semi-translucent scales, and are visible only as darker, light-sensitive spots on the sides of the head. Unlike other snakes they also lack a distinct tail – the body pretty much ends in a cloaca and all that remains of the tail is a tiny, sharp spike, their only defensive weapon.

The morphology of the Giant blind snake (Megatyphlops schlegelii) reveals its perfect adaptation for subterranean life – there is no neck or distinct tail, which means that the animal can move as easily forward as backward in the underground tunnels; notice the sharp defensive spike at the end of the body.

Needles to say, blind snakes are completely harmless. They produce no venom and may even lack teeth in either the upper or lower jaw. When caught they try to jab the attacker with the tip of the tail, which is about as effective a defense as being licked by a puppy. Still, the firstMegatyphlops I saw in Gorongosa was an animal being hacked to bits by villagers afraid of its (imaginary) venom.

The body of blind snakes is glossy smooth, reducing friction when moving underground. It also makes holding them in your hand rather difficult.

So far I have found three species of blind snakes in the park, usually while flipping rocks when looking for crickets. Interestingly, I have also seen them frequently on the surface at night, moving slowly and deliberately, as if looking for something. These snakes feed mostly on termites and ants, the nests of which are often located under rocks and logs. I imagine that it is easier for the snakes to move on the surface to the next rock, than to plow under the surface, which may explain their behavior. Some blind snakes are known to produce pheromones that mimic those of their prey, thus protecting them from attacks by soldier termites and ants. Their feeding mechanism is different from that of other snakes – more evolutionarily derived snakes swallow the prey by alternatively advancing the left and right upper jaw arches (which can move independently) over the prey. But blind snakes don’t have long, independently movable upper jaw and instead “rake” their insect prey into the mouth by stretching and pulling back their short lower (Leptotyphlopidae) or upper (Typhlopidae) jaw. Apparently, smaller species may not even swallow the prey at all, but instead suck the liquid portion of the insect’s body and discard the exoskeleton.